Saad, I must confess I had to lab this one up to prove it to myself as I had a faulty or out-dated memory about this command. Currently under IOS
12.2(23), when applying the IP DEFAULT-NETWORK command to R1 with RIPV2 active, R2 receives a default route - that looks like this:
R2#sho ip route Gateway of last resort is 10.10.1.1 to network 0.0.0.0 10.0.0.0/24 is subnetted, 1 subnets C 10.10.1.0 is directly connected, Ethernet0 R 188.8.131.52/24 [120/1] via 10.10.1.1, 00:00:09, Ethernet0 R* 0.0.0.0/0 [120/1] via 10.10.1.1, 00:00:10, Ethernet0
R1 gets the route flagged with an asterisk but as is a connected route, the Gateway of Last Resort is not set - as follows:
R1#sho ip route Gateway of last resort is not set 10.0.0.0/24 is subnetted, 1 subnets C 10.10.1.0 is directly connected, Ethernet0 C* 184.108.40.206/24 is directly connected, Ethernet1 220.127.116.11/24 is subnetted, 1 subnets R 18.104.22.168 [120/1] via 10.10.1.2, 00:00:06, Ethernet0
The command was applied to R1 as IP DEFAULT-NETWORK 22.214.171.124
Also, my understanding is that this automatic incorporation of the IP DEFAULT-NETWORK into the routing protocol is only extended to RIP and IGRP (both classful routing protocols). And in fact, since IGRP doesn't understand the command IP ROUTE 0.0.0.0 0.0.0.0, the IP DEFAULT-NETWORK command is even more meaningful in IGRP.
This is correct. In RIP, ip default-network xxxxx will advertise a candidate default route (0.0.0.0/0) bit will not install it locally. To have a default network locally on R1, you would have to configure a static route: ip route 0.0.0.0 0.0.0.0 xxxxx
Here is the link:
"Gateways of last resort selected using the ip default-network command are propagated differently depending on which routing protocol is propagating the default route. For IGRP and EIGRP to propagate the route, the network specified by the ip default-network command must be known to IGRP or EIGRP. This means the network must be an IGRP- or EIGRP-derived network in the routing table, or the static route used to generate the route to the network must be redistributed into IGRP or EIGRP, or advertised into these protocols using the network command.
RIP advertises a route to 0.0.0.0 if a gateway of last resort is selected using the ip default-network command."